Orientation discrimination in WS 21
group were transformed into z-scores to give two standardised measures of
performance based on the distribution of scores of the appropriate group of controls.
One participant with WS had taken part in the mental rotation task, but not the
size transformation task, and similarly one individual had been included in the size
transformation task, but not the mental rotation task. The data from these two
individuals were excluded from the analysis. The data remaining was from 20
individuals with WS on each of the mental imagery tasks. Mean z-scores for
performance on the two mental image transformation tasks were: mental rotation
mean= -1.00, S.D. = 0.667; and size transformation mean = -0.255, S.D.=0.667. To
compare WS performance across the two tasks, the z-scores for the two tasks were
subjected to a paired comparison t-test. This demonstrated that level of performance
of the WS group on the size transformation task was significantly superior to that on
the mental rotation task, t(19)=4.36, p<.001.
Discussion
The results of Experiment 2 indicate that individuals with WS behaved in a
comparable way to TD controls on a size transformation task. For both groups there
was a linear effect of the size difference on performance as found in previous
investigations (Besner, 1983; Bundesen & Larsen, 1975; Larsen & Bundesen, 1978).
This is an important finding as it indicates not only that individuals with WS can
perform mental image transformation when assessed using a size transformation task,
but also that they can complete the task to the same level as their typically developing
non-verbal matched peers. One can therefore assume that this ability is available to
individuals with WS when completing a block construction task, and does not
contribute to their particularly poor level of performance on such tasks. In turn, this
suggests that not all aspects of dorsal stream functioning are equally impaired in WS.